To apply newer electromyographic techniques to upper airway muscles with a view towards identifying important therapeutic targets in obstructive sleep apnea. Career development goals: To provide sufficient time for mentoring of trainees and research activities. Research project: Obstructive sleep apnea is an important disease due to its high prevalence and well established neurocognitive and cardiovascular sequelae. Treatment of this disease remains problematic since the existing therapies are either poorly tolerated or have variable efficacy, leading many to advocate for further research into underlying mechanisms. Prior research has established in the importance of the upper airway muscles (such as the genioglossus and tensor palatini) in the pathogenesis of sleep apnea. However, multi-unit electromyographic recordings provide an average representation of innumerable motor units yielding fairly incomplete information about the behavior of individual motor units. We have current R01 funding to perform high frequency sampling of the electromyogram to define the various motor units within the genioglossus muscle. These newer studies have revealed marked complexity in the behavior of the genioglossus muscle, with 6 distinct firing patterns being identifiable. A rise or fall in the genioglossal multiunit EMG is therefore difficult to interpret since these changes could be mediated by any of a number of individual motor unit firing changes. We have observed specific units which may be most critical for the maintenance of pharyngeal patency. Such units would thus we logical therapeutic targets which we can address with our neuroanatomy collaborators. We have also begun studies using single fiber EMGs and MacroEMGs which a view towards performing more quantitative assessments of various upper airway muscles. We will use the K24 funding to focus on clinically relevant findings from the R01 such that ultimately clinicians will be able to define upper airway motor function without the need for complex or invasive physiology testing. This K24 award would allow us to pursue interesting hypotheses which may ultimately lead to new easily applicable treatments for sleep apnea. This award will also allow the PI to dedicate more time to training young investigators in the field of sleep and respiratory physiology by reducing his clinical responsibilities. The need for an investigator pipeline has been termed a crisis (Sleep. 2006 29:1260) which the PI would like to continue to address through his research and his dedication to his trainees.